Solar cells are devices that have characteristics that enable them to convert the energy of sunlight into electric energy. The aim of research often is to achieve solar cell designs and manufacturing methods that are suitable for inexpensive commercial production while providing acceptably high energy conversion efficiencies for the solar cells. A further driving force is how to provide improvements in solar cell reliability, e.g., less degradation in the cell when strained or placed into use, which may be thought of as providing a solar cell that is more stable in its functionality over time.
More generally, thin-film photovoltaic (PV) devices may be used to create solar cells, detectors, electronic devices, telecommunication devices, charge-coupled imaging devices (CCDs), computers, and even biological or medical devices (together considered “thin-film compound semiconducting materials”). With regard to renewable energy, solar cells are devices that have characteristics that enable them to convert the energy of sunlight into electric energy. The aim of research often is to achieve solar cell designs with the lowest cost per watt generated by the solar cell, and, concurrently, the designs should provide solar cells that are suitable for inexpensive commercial production and also provide solar cells with improved reliability.
The potential market for thin-film photovoltaic (PV) devices is enormous and is expected to continue to grow in the coming years. Recently, a goal was set to globally deploy one terawatt of continuous PV-based power, and achieving this goal will require an industry that can supply on the order of 300 to 400 GWp (gigawatt peak) of PV modules each year. Additionally, in the United States, goals concerning costs have been set that include a module-level cost goal for utility-scale PV installations of 0.5 $/Wp, which would make unsubsidized PV competitive with conventional power sources. At this cost level and at a deployment level in the hundreds of GWp per year, PV module sales globally may be in excess of $50 billion (in U.S. dollars) per year. As will be appreciated, any technology that can better enable the PV industry, such as by increasing efficiencies, reducing material costs, lowering manufacturing expenses, and the like, has a large potential for growth and revenue generation.
A conventional thin-film solar cell is composed of a stacking of thin layers (e.g., 0.1 to 2 microns thick) on a substrate, and the thin layers form one or more junctions with differing band gaps that absorb light and convert it into electricity. Presently, most commercially available thin-film solar modules are fabricated with an absorber or absorber layer formed of cadmium telluride (CdTe), which has high optical absorption coefficients and have versatile optical and electrical characteristics.
Cadmium telluride (CdTe) photovoltaics is a term that describes a photovoltaic (PV) technology that is generally based on the use of a CdTe thin-film absorber layer in a device that converts sunlight into electricity. There is an ongoing and even growing interest in the use of CdTe in solar cells and solar panels because CdTe thin films are one of the only thin films to surpass crystalline silicon PV technology in providing lower $/W devices for the PV market including multi-megawatt systems. CdTe thin films are attractive in part because they can be deposited very rapidly upon a glass substrate to provide large PV panels (e.g., a panel with a width limited by a deposition tool but a length often only limited by structural concerns for the substrate) rather than being grown as single crystal devices. However, the reliability of CdTe thin films continues to be a concern within the solar power industry, and researchers continue to search for ways to improve this limiting factor associated with use of CdTe thin films in solar cells.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.